Radio frequency (RF) system and wireless sensor network (WSN) are two technologies integrated to provide a wide variety of applications, particularly where merging the physical world with the digital world (also referred to as the virtual world). For example, where energy-constraints confine network performance of a wireless sensor network, RF energy harvesting schemes can be implemented to provide power (energy) to various nodes of the wireless sensor network, while further extending sensing capabilities of the wireless sensor network. In such scenarios, wireless power is efficiently and optimally transmitted to the various nodes. Although existing wireless power transmission systems and methods in wireless network environments have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects.